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TS DX350HDV

Holydvr

Tony (The Flasher) 1776 NW Arizona
Nov 2, 2018
576
597
103
44
Golden Valley, AZ
Good evening!

I have a 350HDV here that is clicking over to xmit (meter light turns on) as soon as the power switch is turned on. I replaced the keying transistor and the problem still persists, but if the keying transistor is removed, then it will not key itself up when the power switch is turned on. I was suspecting the relay, but it does click back and forth as soon as the power switch is cycled. Anyone ran into this before? Nothing seems to get hot at all like a short, but I am unsure as if yet. I was told it does make power out, just has no receive. No receive us of course due to the relay clicking over as soon as power is turned on.
 
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Are you saying that when you push the power switch to ON, the relay "temporarily" keys up, lights the meter light, and then immediately unkeys and goes back into normal standby ???
 
It's been my experience that Q1 and Q2 "circuits" need to be checked.

One can click the relay, but both need to be checked and the Diodes and the Caps connecting them to their "Sense" lines too.

The RF amp section - when spiked can short out and the relay clicks on because Q2 thinks Q1 is on and conducting - even though its' Receive - so even bias from the amps own "amp" can bleed back thru and turn on the relay because Q1 is thinking something is present on it's sense line...

Check and swap out C1 15pF to be sure...

Seen more than once a spike in the Amps relay - is enough to weld the plates of even the output caps together and act as a short...

This may be the condition - you've spiked a cap or blew a diode.

Cobbled from CB Tricks...
TS350HDVQ1Q2.jpg
 
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Ranch55, no, the amp clicks over when the power button is pushed and stays keyed up as long as power is applied to it.

Handy Andy, I want to thank you very much for the reply! I have read in depth some of your vast amount of knowledge on the PC122. I always wanted to thank you for all you have shared. I guess the day just might have come where I am able to!

Tony
 
Shorted Q1 is incredibly common. Didn't start seeing this failure until radios with RCI-style modulators became common around 30 years ago. When the audio is turned up, the negative modulation peaks become long pulses of "no carrier". This causes the keying transistor to spend too much time in between being fully turned on and fully turned off. When the tiny 2N2907 transistor is turned on by a steady carrier, it has a very low voltage drop across it and runs cool. But when it spends too much time 'in between' fully on and fully turned off, it acts like a resistor and gets hot. But only until it fails as a short and keys the relay as soon as power is applied thereafter.

We found that putting a small electrolytic capacitor in parallel with C2 when Q1 is replaced would stop this. A value between 4.7 and 22 uf does the job without making the relay take longer to unkey.

Got in the habit of putting a 10uf cap across C2 in every Texas Star we see, as a preventive measure even if the customer had no keying-circuit trouble. Much cheaper than the headache of a customer who has trouble down the line.

73
 
I have an old pride 150 bi liniear mobile amp that keys up and stays keyed whenever power is switched on and the relays are not stuck and the key transistor taken out it does not key up and the key transistor is still good it tested good but the sockets where it came from in the amp are all 3 shorted to eachother.
Is this a possible spike to ? I tried to transmit a radio through it when powered on as the box transmits by itself i key down radio nothing comes out and the receive going through it when box is turned off is not too good and the radios transmit is also 5 watts lower from the radio going through the amp while turned off.
 
I remember that amplifier as having big open-frame 3-pole relays in it. When they get dirty, some folks will try to "adjust" the contact levers by warping them. The contact points contain some silver, so cleaning the tarnish from them may help. Don't use any kind of abrasive. Cut a strip of copy paper to draw across the contacts. First wet the paper with 99% isopropyl, CRC "QD" cleaner from AutoZone, or other non-residue solvent. Thread it under the receive-side contacts, and draw it across them. If you see a dark streak on the paper, cut another strip and repeat. When a strip comes out with little or no darkening, you're done. Same procedure for the transmit-side, but hold the armature down to put some friction onto the contact surfaces as the paper draws across them.

And if someone has warped the relays' lever arms, you just need to replace the relay.

Don't want to underestimate how many different things could be wrong with an amplifier that's probably over 40 years old.

It's rare for anything that old to have "just one" thing wrong with it.

You said that all three connections for the keying transistor on the circuit board show shorted with the transistor removed. Too many ways for that to happen, starting with damage to the foil traces on the bottom side where you can't see.

The more people that have worked on it, the more stuff like damaged foil traces you're likely to find.

73
 
Last edited:
I remember that amplifier as having big open-frame 3-pole relays in it. When they get dirty, some folks will try to "adjust" the contact levers by warping them. The contact points contain some silver, so cleaning the tarnish from them may help. Don't use any kind of abrasive. Cut a strip of copy paper to draw across the contacts. First wet the paper with 99% isopropyl, CRC "QD" cleaner from AutoZone, or other non-residue solvent. Thread it under the receive-side contacts, and draw it across them. If you see a dark streak on the paper, cut another strip and repeat. When a strip comes out with little or no darkening, you're done. Same procedure for the transmit-side, but hold the armature down to put some friction onto the contact surfaces as the paper draws across them.

And if someone has warped the relays' lever arms, you just need to replace the relay.

Don't want to underestimate how many different things could be wrong with an amplifier that's probably over 40 years old.

It's rare for anything that old to have "just one" thing wrong with it.

You said that all three connections for the keying transistor on the circuit board show shorted with the transistor removed. Too many ways for that to happen, starting with damage to the foil traces on the bottom side where you can't see.

The more people that have worked on it, the more stuff like damaged foil traces you're likely to find.

73
Strange I have a couple of Pride amps a 150 and a 100 and both of them have enclosed relays two of them in each.
 
It's altogether possible that I'm remembering the wrong amplifier. For that matter, how many different outfits "borrowed" the Pride name? More than one, best I can tell. Good chance his amplifier is one I haven't seen before.

73
 

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